Bellarmine's certificate, and the Minute of 3 March seem to indicate that Galileo was under no absolute prohibition. Nevertheless, during the next few years he had to proceed more cautiously than before.
II THE TRIAL OF GALILEO
1. The Tides
AFTER the issue had been formally decided by the decree of 5 March, Galileo stayed on in Rome for another three months. "He is of a fixed humour," the Tuscan Ambassador reported, "to tackle the friars head on, and to fight personalities who cannot be attacked without ruining oneself. Sooner or later you will hear in Florence that he has madly tumbled into some unsuspected abyss." 1 In the end, the alarmed Duke ordered Galileo back to Florence.
For the next seven years he published nothing. But his obsession was devouring him. It was the more self-destructive because he could not vent it. He could mutter about "the ignorance, malice and impiety of my opponents who had won the day"; but he must have known, without admitting it to himself, that his defeat was really due to the fact that he had been unable to deliver the required proof.
This, I suggest, explains how the delusion about the tides could gain such power over his mind. He had improvised this secret weapon in a moment of despair; one would have expected that once he reverted to a normal frame of mind, he would have realized its fallacy and shelved it. Instead, it became an idée fixe, like Kepler's perfect solids. But Kepler's was a creative obsession: a mystic chimera whose pursuit bore a rich and unexpected harvest; Galileo's mania was of the sterile kind. The tides, as I shall presently try to show, were an indirect substitute for the stellar parallax which he had failed to find – a substitute not only in the psychological sense, for there exists a mathematical connection between the two, which seems to have eluded attention so far.
Galileo's theory of the tides runs, in a slightly simplified form, as follows. 2 Take a point on the earth's surface – say, Venice. It has a two-fold motion: the daily rotation round the earth's axis, and its annual revolution round the sun. At night when Venice is at N, the two motions add up; in daytime, at D, they work against each other:
Hence Venice, and with it all the firm land, moves faster at night and slower in the daytime; as a result, the water is "left behind" at night, and rushes ahead of the land in daytime. This causes the water to get heaped up in a high tide every twenty-four hours, always around noon. The fact that there are two daily high tides at Venice instead of one, and that they wander round the clock, Galileo dismissed as due to several secondary causes, such as the shape of the sea, its depth, and so forth.
The fallacy of the argument lies in this. Motion can only be defined relative to some point of reference. If the motion is referred to the earth's axis, then any part of its surface, wet or dry, moves at uniform speed day and night, and there will be no tides. If the motion is referred to the fixed stars, then we get the periodic changes on the diagram, which are the same for land and sea, and can produce no difference in momentum between land and sea. A difference in momentum, causing the sea to "swap over" could only arise, if the earth received a push by an external force – say, collision with another body. But both the earth's rotation and its annual revolution are inertial, 3 that is, self-perpetuating, and hence produce the same momentum in water and land; and a combination of the two motions still results in the same momentum. The fallacy in Galileo's reasoning is that he refers the motion of the water to the earth's axis, but the motion of the land to the fixed stars. In other words, he unconsciously smuggles in the absent parallax through the back door. No effect of the earth's annual motion relative to the fixed stars could be found. Galileo finds it in the tides, by bringing the fixed stars in where they do not belong. The tides became an Ersatz for parallax.
The power of the obsession may be judged by the fact that, although a pioneer in the field of the relativity of motion, he never discovered the elementary error in his reasoning; seventeen years after he had hit on his secret weapon, he still firmly believed that it was the conclusive proof of the motion of the earth, and presented it as such in his Dialogue on the Great World Systems. He even intended to name that work Dialogue on the Flux and Reflux of the Tides.
2. The Comets
The next two years he was mostly ill, but did some minor work, such as the construction of a naval telescope, and also made an attempt, which failed, to use the periods of the Jupiter moons as an aid to determine geographical longitude. It was apparently the last time he took a positive interest in astronomical research.
After two years, in 1618, he could hold back no longer, and sent his treatise on the tides to Archbishop Leopold of Austria, describing it in his covering letter as a "poetical conceit or dream" written at the time when he believed the Copernican system to be true, and before being taught better by the decision of the authorities who were "guided by a higher insight than any to which my humble mind can of itself attain." He hoped, no doubt, that the treatise would be printed in Austria without formal authorization on his part, but it came to nothing.
In the same year three comets appeared in the sky. They announced the beginning both of the Thirty Years War, and of the most disastrous of the many controversies in which Galileo became involved.
It was caused by a lecture, subsequently published, by the Jesuit Father Horatio Grassi of the Collegium Romanum. It expressed the correct view that comets move in regular orbits like planets, at a distance far greater than the moon's. In support of this view, Grassi quoted with approval Tycho's conclusions regarding the famous comet of 1577. The treatise was a further step in the Jesuits' retreat from Aristotle, who had maintained that comets were earthly exhalations in the sublunary sphere, and a further sign of the Order's implicit endorsement of the Tychonic system.
When Galileo read the treatise, he had an outburst of fury. He covered its margins with exclamations like "piece of asininity", "elephantine", "buffoon", "evil poltroon", and "ungrateful villain". The ingratitude consisted in the fact that the treatise did not mention Galileo's name – whose only contribution to the theory of comets had been a casual endorsement of Tycho's views in the Letters on Sunspots. 4
But now the situation had changed. The Tychonic compromise must be rejected, so that the choice should remain confined to the discredited Ptolemy and to Copernicus. Galileo abruptly reversed his own arguments: he decided that comets are not real objects at all, but optical illusions like the aurora-borealis or the mock-suns, caused by the reflection of earthly vapours, which reach up into the sky past the moon. If they were real, they ought to appear larger as they approach the earth and smaller as they recede, whereas, according to Galileo, comets appear at their full size and then vanish altogether.
Apart from wishing to prove that Tycho and Grassi understood nothing of astronomy, Galileo had another motive for denying that comets exist: their paths were so markedly elliptic, that they could not be reconciled with the circular orbits in which all real heavenly objects must move around the sun.
Galileo did not attack Grassi directly, under his own name, but let his former pupil Mario Guiducci, sign a Discourse on Comets – the manuscript of most of which survived, and is in Galileo's handwriting. At the end of the treatise, Grassi is reproached for failing to mention Galileo's discoveries, and Father Scheiner for "misappropriating the discoveries of others".
Since Galileo had not signed with his own name, Grassi now replied under a transparent anagram as "Lothario Sarsi Sigensano" (for Horatio Grassi Salonensi). He ignored Guiducci, and attacked Galileo with vehemence. He showed that Galileo claimed priority for discoveries which were not his own, and took up the challenge about the Tychonic system: since Ptolemy was refuted and Tycho rejected by Galileo, does he mean that Grassi should have endorsed Copernicus, condemned and abhorred by every good Catholic?
Grassi's pamphlet was published in 1619 under the title The Astronomical and Philosophical Balance. Galileo's answer was the famous Il Saggiatore – The Assayer, who measures things on the finer balance designed for precious metals. It took him two yea
rs to write it, and it was published in 1623 only, four years after Grassi's counter-attack.
The Assayer was written in the form of a letter to a friend, Monsignor Cesarini, Chamberlain to the Pope. It starts with a tirade against all who tried to rob Galileo "of the glory of his discoveries", to whose ranks he now added Marius von Gunzenhausen, the discoverer of the spiral nebula in Andromeda (the first nebula observed). It is in this context that the passage occurs which I have quoted already:
"You cannot help it, Signor Sarsi, that it was granted to me alone to discover all the new phenomena in the sky and nothing to anybody else. This is the truth which neither malice nor envy can suppress."
The Assayer then sets out to demolish the reputation of Tycho by talking of his "alleged observations", and by calling comets "Tycho's monkey-planets". He also explains the reason which forced him to break his previous resolve to publish no more: Galileo's enemies, having unsuccessfully tried to steal his discoveries, now try to attribute to him "the works of others" – namely, Guiducci's tract. He indignantly denies having had any part in that tract beyond discussing the subject with Guiducci; but now he has to break his silence "to discourage those who refuse to let sleeping dogs lie, and who stir up trouble with men that are at peace".
The major part of the work consists of sarcastic refutations of everything Grassi had said, regardless whether the poor man had blundered – which he often had – or hit on the truth. Thus Grassi had maintained that projectiles get heated by friction with the air; Galileo answered that they got not hotter but colder: "trying to pulverise the air is as great a waste of time as grinding water in the proverbial mortar". 5 As it so often happens, Grassi had tried to prove a good case by a bad argument: he quoted Suidas (a tenth century Greek lexicographer) to the effect that the Babylonians cooked eggs by whirling them swiftly through the air on a sling. This gave Galileo an opportunity of making mincemeat of his opponent in a hilarious passage which is often quoted, (but mostly without mention of the context):
"If Sarsi wants me to believe with Suidas that the Babylonians cooked their eggs by whirling them in slings, I shall do so; but I must say that the cause of this effect was very different from what he suggests. To discover the true cause I reason as follows: 'If we do not achieve an effect which others formerly achieved, then it must be that in our operations we lack something that produced their success. And if there is just one single thing we lack, then that alone can be the true cause. Now we do not lack eggs, nor slings, nor sturdy fellows to whirl them; yet our eggs do not cook, but merely cool down faster if they happen to be hot. And since nothing is lacking to us except being Babylonians, then being Babylonians is the cause of the hardening of eggs, and not friction of the air.'" 6
But in between these brilliant irrelevancies and sophistries, there are again passages scattered about which have become classics of didactic literature. They concern the principles of scientific reasoning, experimental procedure, the philosopher's duty to be sceptical about authorities and principles that are being taken for granted. Above all, Galileo outlines a principle which became of outstanding importance in the history of thought: the distinction between primary qualities in nature such as the position, number, shape and motion of bodies, and secondary qualities such as colours, odours, and tastes, which are said to exist only in the observer's consciousness. 7
"To excite in us tastes, odours, and sounds I believe that nothing is required in external bodies except shapes, numbers, and slow or rapid movements. I think that if ears, tongues, and noses were removed, shapes and numbers and motions would remain, but not odours or tastes or sounds. The latter, I believe, are nothing more than names when separated from living beings..."
Though anticipated by the Greek atomists, it is for the first time in the modern age that this distinction is made in such concise terms, the first formulation of the mechanistic view of the universe. But on most contemporary readers of The Assayer the significance of that passage was lost. They saw Galileo only in the role of the toreador, and the consensus was that Father Grassi had to be dragged out of the arena sprawling on his back.
Grassi was a prominent Jesuit scholar, and not at all the fool that Galileo made him out to be. He had drawn the plans for the Church of St. Ignazio in Rome and had designed a submarine, based on a suggestion of Leonardo's. The treatment meted out to him, added to the equally unprovoked attacks upon Scheiner, turned these two influential members of the Jesuit Order into implacable enemies of Galileo. A third Jesuit whom he had attacked without necessity (on a question of military engineering, of all things) was Father Firenzuola, who built the fortifications of the Castle St. Angelo. Twenty-five years later, Firenzuola was the Inquisition's Commissary General at Galileo's trial. The result of all this was that the Jesuits as a body turned against Galileo. Father Grienberger, who succeeded Clavius as head of the Roman College, was to remark later that "if Galileo had not incurred the displeasure of the Company, he could have gone on writing freely about the motion of the earth to the end of his days." 8
The clash with the Aristotelians was inevitable. The clash with the Jesuits was not. This is not meant as an apology for the vindictiveness with which Grassi and Scheiner reacted when provoked, nor of the deplorable manner in which the Order displayed its esprit de corps. The point to be established is that the attitude of the Collegium Romanum and of the Jesuits in general changed from friendliness to hostility, not because of the Copernican views held by Galileo, but because of his personal attacks on leading authorities of the Order.
Other great scientists, including Newton, became embroiled in bitter polemics. But these were peripheral to their work, skirmishes around a solidly established position. The particular tragedy of Galileo was that his two major works were only published after his seventieth year. Up to then, his output consisted in pamphlets, tracts, manuscripts circulated privately, and oral persuasion – all of it (except the Star Messenger) polemical, ironically aggressive, spiced with arguments ad hominem. The best part of his life was spent in these skirmishes. Until the end he had no fortress in the form of a massive and solid magnum opus to fall back upon. The new conception of science and philosophy which he brought into the world is diffused in passages here and there among the polemics of the Letters on Sunspots or The Assayer – hidden between tangles of barbed wire, as Kepler's laws were among his harmonic labyrinths.
3. Dangerous Adulation
While he was writing Il Saggiatore, Galileo's loyal patron, Cosmo II, died and the formidable Dowager Christina became Regent. Bellarmine, who had been a restraining influence at the head of the Jesuit Order, died in the same year. But against these losses, fate threw into the assayer's balance the most unexpected and powerful ally: Maffeo Barberini was elected to the papacy in 1623 – just in time for Galileo to dedicate Il Saggiatore to him.
Maffeo Barberini was something of an anachronism: a Renaissance Pope transplanted into the age of the Thirty Years War; a man of letters who translated passages from the Bible into hexameters; cynical, vainglorious, and lusting for secular power. He conspired with Gustavus Adolphus, the Protestant heretic, against the Holy Roman Empire; and on learning of the death of Richelieu, remarked: "If there is a God, Cardinal Richelieu will have much to answer for; if not, he has done very well." He fortified the Castle St. Angelo, and had guns cast out of the bronze ceilings of the Pantheon – which gave rise to the epigram: "What the barbarians have not done, Barberini did." He founded the "Office of the Propaganda" (for missionaries), built the Barberini Palace, and was the first Pope to allow a monument to be erected to him in his lifetime. His vanity was indeed monumental, and conspicuous even in an age which had little use for the virtue of modesty. His famous statement that he "knew better than all the Cardinals put together" was only equalled by Galileo's that he alone had discovered everything new in the sky. They both considered themselves supermen and started on a basis of mutual adulation – a type of relationship which, as a rule, comes to a bitter end.
Ba
ck in 1616, Barberini had opposed the decree of the Congregation and intervened in favour of Galileo, a fact of which he often boasted later on. In 1620, he had written an ode in honour of Galileo, with the title Adulatio Perniciosa – which may be translated as "Perilous Adulation". He even went so far as to pay homage to the memory of Copernicus – in an audience with Cardinal Hohenzollern in 1624, after he had become Pope – and added the remark that "the Church neither had condemned, nor ever would condemn his doctrine as heretical, but only as reckless." 9
When Urban was installed, there began a kind of second honeymoon between the repository of Faith and the foremost representative of Science in Italy. Renuncini, a brother of Cardinal Dini, wrote to Galileo:
"I swear to you that nothing pleased his Holiness so much as the mention of your name. After I had been speaking of you for some time, I told him that you, esteemed Sir, had an ardent desire to come and kiss his toe, if his Holiness would permit it, to which the Pope replied that it would give him great pleasure, if it were not inconvenient to you ... for great men like you must spare themselves, that they may live as long as possible." 10
Galileo was ill, so he could only journey to Rome in the spring of the next year. He had six long audiences with Urban in the course of six weeks. The Pope showered favours on him: a pension for Galileo's son, a precious painting, a gold and silver medal. He also provided him with a glowing testimonial, addressed to the new Grand Duke, extolling the virtues and piety "of this great man, whose fame shines in the heavens, and goes on earth far and wide."